1. Field of the Invention
The invention relates to a folding umbrella comprising a canopy-supporting framework with a plurality of linkages each including a pair of rod parts which extend alongside one another and are guided for relative longitudinal displacement by an integral bent part of one of the rod parts, which rod part is made of wire, engaging around the other rod part. Such a frame is hereinafter referred to as of the kind described.
2. Description of Related Art
An umbrella of this general character is known, for example, from U.S. patent specification No. 4,966,180 and from Taiwan UM Publication 143761. In both cases, two canopy rod parts, which extend approximately parallel to one another and which are guided so as to be displaceable on one another, form the long links of a lever parallelogram. Of the latter, the control link is made of thin wire for the purpose of achieving an optimally thin or small dimensioned folded structure of the closed umbrella and, moreover, a helix is also additionally formed in the wire, by means of which the control link is supported so as to be displaceable on the more stable parallel link. In U.S. Pat. No. '180, the helix is shown as a loose coil whereas, according to the TW '761, it is constructed as a multi-turn coil. In both cases, the coil serves not only for supporting and stabilising on the parallel link the unstable thin control link which is nevertheless considerably stressed in terms of compression and tension, but also, for reasons of saving costs, for dispensing with a separate specific guide element, such as is represented, for example, as a bush guide in FIG. 1 of the U.S. Pat No. '180, for example, as shown in U.S. patent specifications Nos. 4,739,783 (FIG. 4) or 4,676,262 (FIG. 5).
In particular the guide according to the latter cited patent specification likewise does not require a separate part as a result of a material squeezing of the profile of the parallel link, which squeezing encloses the thin control link in a displaceable manner. However, since this squeezing causes an undesired weakening of this link, this variant of a support and guide of the unstable control link is not practical. However, the supports and guides described above by means of the coil according to U.S. Pat. No. '180 and TW '761 respectively are also not practical. On the one hand, the unstable control link made of thin wire is intended to be supported with the aid of these guides for the purpose of stabilisation and in order to maintain the required rigidity against tensile and compression stresses. At the same time, the supporting guide is to be of an optimally inexpensive and simple design with the aid of the coil. However, this coil acts counter to the latter and in a counter-productive manner since, by nature, they act as a coil spring to damp and destroy the tensile and compression force in a linear manner and thus, at least to a considerable extent, do not transmit the tensile and compression forces acting at one end of the control link. Accordingly, the entire function of the umbrella is in doubt.